Supercharger pressure control system for internal combustion engine with turbocharger

Abstract

The supercharger pressure control system includes a sensor for detecting the supercharger pressure of the engine and regulates the pressure through a variable geometry device or an exhaust bypass valve. The control for the pressure regulation is carried out by comparing the sensed supercharge pressure with a target value. Any difference determined by this comparison is accumulated by a computer as an error and a basic control value is determined based on the error. Alternatively, a predetermined basic control value for the engine intake air is corrected in accordance with the error and this control value or corrected value is used to control the operation of the supercharge pressure regulator. This causes the regulator to operate in a manner responsive to variations in performance of the engine or turbocharger, thus maintaining the supercharged pressure within a permissible range of a target value.

What is claimed is: 
     
       1. A supercharge pressure control system for an internal combustion engine with a turbocharger comprising: means for detecting the supercharge pressure of the engine;   regulating means having at least one of a variable geometry means and an exhaust bypass means, for regulating the supercharge pressure of the engine; and   control means for inputting the detected supercharge pressure from the detecting means and for selecting a specific control value based on an intake air flow of the engine in accordance with an accumulated value of a difference between the detected supercharge pressure and a target supercharge pressure, said accumulated value being calculated for each of the variable geometry means and the exhaust bypass means, said control means outputting a suitable control value, based on the specific control value, for controlling the supercharge pressure to each of the variable geometry means and the exhaust bypass means.   
     
     
       2. A supercharged pressure control system according to claim 1 in which the suitable control value is obtained by selecting one of the suitable of control tables, and selecting a particular control value from said selected table. 
     
     
       3. A supercharged pressure control system according to claim 2 in which said plurality of control tables contain inflow characteristics of intake air. 
     
     
       4. A supercharged pressure control system according to claim 1 in which the suitable control value is obtained by correction of a predetermined basic control value. 
     
     
       5. A supercharged pressure control system according to claim 4 in which and the basic control value and a correction value are given in terms of inflow characteristic of intake air to the engine. 
     
     
       6. A supercharged pressure control system according to claim 1 in which the pressure difference is accumulated over a plurality of segmented air flow rate regions. 
     
     
       7. A supercharged pressure control system according to claim 1 in which said variable geometry means comprises variable value means disposed in an inlet of the turbine and said exhaust bypass means comprises variable bypass valve means disposed in an exhaust gas outlet of the engine. 
     
     
       8. A supercharged pressure control system according to claim 7 in which in a region where operating regions of the variable valve means and the variable bypass valve means overlap each other, the variable valve means is opened to the greatest degree allowed within a permissible range of the accumulated difference while the variable bypass valve means is closed to the greatest degree allowed within the permissible range of the accumulated difference. 
     
     
       9. A supercharged pressure control system according to claim 1, wherein a correction value is based on the accumulated difference value and is added to or subtracted from a duty value to obtain a new duty value. 
     
     
       10. A supercharged pressure control system according to claim 1, wherein a duty value is obtained by selecting one of a plurality of control tables, said selection being based upon said accumulated value, and selecting the duty value from said selected table. 
     
     
       11. A method for controlling a supercharge pressure in an internal combustion engine with a turbocharger, said method comprising the steps of: detecting the actual supercharge pressure of the engine;   accumulating a difference between the actual supercharge pressure and a target supercharge pressure, said accumulated difference being calculated for at least one of a variable geometry means and an exhaust bypass means for regulating the supercharge pressure of the engine;   selecting a specific control value based on an intake air flow of the engine in accordance with the accumulated difference; and   calculating a suitable control value based on the specific control value for controlling the supercharge pressure with respect to each of the variable geometry means and the exhaust bypass means.   
     
     
       12. A method for controlling a supercharge pressure according to claim 11, wherein said method further comprises the steps of: selecting a correction value based on the accumulated difference;   adding said correction value to a basic duty value when the actual supercharge pressure is greater than the target supercharge pressure to obtain a corrected basic duty value; and   subtracting said correction value from the basic duty value when the actual supercharge pressure is lower that the target supercharge pressure to obtain the corrected basic duty value.   
     
     
       13. A method of controlling a supercharged pressure according to claim 11 in which control of the supercharged pressure regulator is achieved by selecting a specific one of a plurality of preset control tables and deriving said specific control value from the specific control table. 
     
     
       14. A method of controlling a supercharged pressure according to claim 11 in which control of the supercharged pressure regulator is achieved by correcting a predetermined basic control value and using the corrected basic control value. 
     
     
       15. A method of controlling a supercharged pressure according to claim 13 in which the plurality of control tables are based upon at least an intake air flow rate of the engine. 
     
     
       16. A method of controlling a supercharged pressure according to claim 11, wherein said method further comprising the steps of: (a) calculating an air flow rate per revolution of the engine,   (b) calculating an accumulated difference between the actual and the target supercharged pressure over a plurality of segmented air flow rate regions,   (c) determining a table number based upon the accumulated difference,   (d) determining a duty value by a table lookup operation with respect to a table having the table number, said table containing predetermined duty values for selected values of the air flow rate per revolution and the number of revolutions of the engine,   (e) and choosing the determined duty value when it is within a predetermined range and choosing either the maximum value or minimum value of the predetermined range when the determined duty value is outside of the predetermined range for use in controlling the supercharged pressure regulator means.   
     
     
       17. A method of controlling a supercharged pressure according to claim 11 said method further comprising the steps of: (a) calculating an air flow rate per revolution of the engine,   (b) calculating the accumulated difference between the actual and the target supercharged pressure over a plurality of segmented air flow rate regions,   (c) determining a basic duty value by a table lookup operation with respect to a table which contains predetermined duty values for selected values of the number of revolutions of the engine and the air flow rate per revolution,   (d) and determining a correction value in accordance with the accumulated difference, and combining the correction value with the basic duty value to provide a corrected duty value which is used in controlling the supercharged pressure regulator means.   
     
     
       18. A method of controlling a supercharged pressure according to claim 11 in which said variable geometry means comprises variable valve means disposed in the inlet of the turbine and said exhaust bypass means comprises variable bypass valve means disposed in the exhaust gas outlet of the engine. 
     
     
       19. A method of controlling a supercharged pressure according to claim 18 in which a control procedure is employed where the variable valve means and the variable bypass valve means operate in an overlapped manner, the control procedure comprising the steps of: (a) slightly increasing the opening of the variable valve means to see if the lower limit of the supercharged pressure is determined by the variable valve means or the variable bypass valve means,   (b) determining, when it is found at step (a) that the lower limit is determined by the variable valve means, if the accumulated difference is within a permissible range,   (c) if it is found at step (b) that the accumulated difference is not within the permissible range, opening or closing the variable valve means until the accumulated value comes into the permissible range, and if it is found that the accumulated difference is within the permissible range, opening the variable bypass valve means as long as the accumulated difference does not decrease and closing the variable bypass valve means when the accumulated difference decreases,   (d) if it is found at step (a) that the lower limit is not determined by the variable valve means, determining if the accumulated difference is within the permissible range,   (e) if it is found at step (d) that the accumulated difference is not within the permissible range, opening or closing the variable bypass valve means until the accumulated difference comes into the permissible range, and   (f) if it is found at step (d) that the accumulated difference is within the permissible range, opening the variable valve means as long as the accumulated difference does not decrease and closing the variable valve means when the accumulated difference decreases.   
     
     
       20. A supercharge pressure control system for an internal combustion engine with a turbocharger comprising: means for detecting the supercharge pressure of the engine;   regulating means having at least one of a variable geometry means and an exhaust bypass means, for regulating the supercharge pressure of the engine; and   control means for inputting the detected supercharge pressure from the detecting means and for selecting a specific control value based on an intake air flow of the engine in accordance with an accumulated value of a difference between the detected supercharge pressure and a target supercharge pressure, said accumulated value being calculated for each of the variable geometry means and the exhaust bypass means, said control means outputting a suitable control value which is obtained by selecting one of a plurality of control tables, and selecting the suitable control value from said selected table for controlling the supercharge pressure to each of the variable geometry means and the exhaust bypass means.   
     
     
       21. A supercharge pressure control system for an internal combustion engine with a turbocharger comprising: means for detecting the supercharge pressure of the engine;   regulating means having at least one of a variable geometry means and an exhaust bypass means, for regulating the supercharge pressure of the engine; and   control means for inputting the detected supercharge pressure from the detecting means and for selecting a specific control value based on an intake air flow of the engine in accordance with an accumulated value of a difference between the detected supercharge pressure and a target supercharge pressure, said accumulated value being calculated for each of the variable geometry means and the exhaust bypass means, said control means outputting a suitable control value which is obtained by correction of a predetermined basic control value, for controlling the supercharge pressure to each of the variable geometry means and the exhaust bypass means.   
     
     
       22. A supercharge pressure control system for an internal combustion engine with a turbocharger comprising: means for detecting the supercharge pressure of the engine;   regulating means having at least one of a variable geometry means and an exhaust bypass means, for regulating the supercharge pressure of the engine; and   control means for inputting the detected supercharge pressure from the detecting means and for selecting a specific control value based on an intake air flow of the engine in accordance with an accumulated value of a difference between the detected supercharge pressure and a target supercharge pressure, this pressure difference being accumulated over a plurality of segmented air flow rate regions, said accumulated value being calculated for each of the variable geometry means and the exhaust bypass means, said control means outputting a suitable control value, based on the specific control value, for controlling the supercharge pressure to each of the variable geometry means and the exhaust bypass means.   
     
     
       23. A method for controlling a supercharge pressure in an internal combustion engine with a turbocharger, said method comprising the steps of: detecting the actual supercharge pressure of the engine;   accumulating a difference between the actual supercharge pressure and a target supercharge pressure, said accumulated difference being calculated for at least one of a variable geometry means and an exhaust bypass means for regulating the supercharge pressure of the engine;   selecting a specific one of a plurality of preset control tables and deriving said specific control value from the specific control table based upon an intake air flow and the accumulated difference; and   calculating a specific control value based on the specific control value for controlling the supercharge pressure with respect to each of the variable geometry means and the exhaust bypass means.   
     
     
       24. A method for controlling a supercharge pressure in an internal combustion engine with a turbocharger, said method comprising the steps of: detecting the actual supercharge pressure of the engine;   accumulating a difference between the actual supercharge pressure and a target supercharge pressure, said accumulated difference being calculated for at least one of a variable geometry means and an exhaust bypass means for regulating the supercharge pressure of the engine;   selecting a specific control value based on an intake air flow of the engine in accordance with the accumulated difference; and   correcting a predetermined basic control value and using the corrected basic control value for controlling the supercharge pressure with respect to each of the variable geometry means and the exhaust bypass means.   
     
     
       25. A method for controlling a supercharge pressure in an internal combustion engine with a turbocharger, said method comprising the steps of: detecting the actual supercharge pressure of the engine;   accumulating a difference between the actual supercharge pressure and a target supercharge pressure, said accumulated difference being calculated for at least one of a variable geometry means and an exhaust bypass means for regulating the supercharge pressure of the engine;   selecting a specific control value based on an intake air flow of the engine in accordance with the accumulated difference;   calculating a suitable control value based on the specific control value for controlling the supercharge pressure with respect to each of the variable geometry means and the exhaust bypass means;   calculating an air flow rate per revolution of the engine;   calculating an accumulated difference between the actual and the target supercharged pressure over a plurality of segmented air flow rate regions;   determining a table number based upon the accumulated difference;   determining a duty value by a table lookup operation with respect to a table having the table number, said table containing predetermined duty values for selected values of the air flow rate per revolution and the number of revolutions of the engine; and   choosing the determined duty value it is within a predetermined range and choosing either the maximum value or minimum value of the predetermined range when the determined duty value is outside of the predetermined range for use in controlling the supercharged pressure regulator means.   
     
     
       26. A method for controlling a supercharge pressure in an internal combustion engine with a turbocharger, said method comprising the steps of: detecting the actual supercharge pressure of the engine;   accumulating a difference between the actual supercharge pressure and a target supercharge pressure, said accumulated difference being calculated for at least one of a variable geometry means and an exhaust bypass means for regulating the supercharge pressure of the engine;   selecting a specific control value based on an intake air flow of the engine in accordance with the accumulated difference;   calculating a suitable control value based on the specific control value for controlling the supercharge pressure with respect to each of the variable geometry means and the exhaust bypass means;   calculating an air flow rate per revolution of the engine;   calculating the accumulated difference between the actual and the target supercharged pressure over a plurality of segmented air flow rate regions;   determining a basic duty value by a table lookup operation with respect to a table which contains predetermined duty values for selected values of the number of revolutions of the engine and the air flow rate per revolution; and   determining a correction value in accordance with the accumulated difference, and combining the correction value with the basic duty value to provide a corrected duty value which is used in controlling the supercharged pressure regulator means.